1. Field of the Invention
This invention relates to a parallel to serial code converters for receiving digital information in parallel form and transmitting it in serial form, and in particular, to an altimeter code converter that converts parallel Gray code to serial binary code.
2. Description of the Prior Art
One method of obtaining a parallel-to-serial conversion is by use of shift registers and a general purpose computer. The shift registers convert the parallel Gray code to a serial Gray code that is input to a computer having an algorithm that converts the serial Gray code altimeter information into serial binary code having the same information. This information is then processed by other devices requiring a serial binary input for display, et cetera.
The Gray code output of the altimeter is divided into two sections, the seven high order bits which designate the altitude in 500 foot increments and the three low order bits, which when properly decoded, represent 100 foot increments. Straight Gray code to binary code is not possible for two reasons. First, the zero Gray code output of the altimeter represents an altitude of -1000 feet which means some arithmetic or special decoding has to be performed in order to obtain the correct altitude in 500 foot increments. Second, because the three low order bits represent the altitude in 100 foot increments special decoding would also be necessary to determine whether 0, 100 or 200 feet should be added or subtracted to the corrected 500 foot increment.
Although the above devices accomplish the intended purpose, it is extremely expensive because of the use of a general purpose computer and the required programming associated therewith. Additionally, a non-controllable time delay occurs because of the general purpose computer as the data flow is governed by the computer's conversion time. Therefore, it is clearly evident that a converter which is not only less expensive to produce and operate than converters of the past, but also operating at a greater operating speed would be highly desirable.